Business Segments - Schedule of Financial Information Relating to Industry Segments (Details) - USD ($)	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Apr. 30, 2019
Total net revenue	$ 3,552,000	$ 3,429,000
Total income from operations	910,000	773,000
Total depreciation and amortization	89,000	83,000
Total capital expenditures	169,000
Total assets	44,046,000	43,027,000	$ 43,027,000
Security Alarm Products [Member]
Total net revenue	2,830,000	2,150,000
Total income from operations	725,000	485,000
Total depreciation and amortization	23,000	10,000
Total capital expenditures	169,000
Total assets	6,369,000	6,179,000
Cable & Wiring Tools [Member]
Total net revenue	536,000	679,000
Total income from operations	137,000	153,000
Total depreciation and amortization	31,000	31,000
Total capital expenditures
Total assets	2,725,000	2,713,000
Other Products [Member]
Total net revenue	186,000	600,000
Total income from operations	48,000	135,000
Total depreciation and amortization	20,000	27,000
Total capital expenditures
Total assets	864,000	842,000
Corporate General [Member]
Total depreciation and amortization	15,000	15,000
Total capital expenditures
Total assets	$ 34,088,000	$ 33,293,000